Ulcerative colitis (UC) and Crohn's disease (CD) are the predominant chronic, inflammatory bowel diseases (IBD) in humans. These disorders are autoimmune in nature and occur in the absence of infection. IBD effects up to 2,000,000 Americans (increasing ˜15% annually) and it is associated with unacceptably high rates of morbidity and mortality. IBD is also a significant burden on the U.S. health care system as the most effective treatments are biological drugs that are quite costly.
IBD occurs as the result of inappropriate immune responses in genetically susceptible individuals mediated by complex interactions between environmental stimuli, microbial factors, and the intestinal immune system. The hallmark of IBD is represented by excessive immune responses that mediate gastrointestinal tissue damage, either directly or through the release of soluble, pro-inflammatory mediators.
T cells are a type of immune cell that infiltrate the intestinal mucosa and are key drivers of gastrointestinal tissue damage in IBD. These cells persist and accumulate in the intestinal mucosa because normal physiologic mechanisms designed to censor or eliminate activated T cells are inoperative in the context of IBD. While the exact basis for T cell accumulation in IBD is not fully elucidated, chronic activation by microbial stimuli along with the cytokine milieu at the sites of inflammation within gastrointestinal tissue are thought to be important. Regardless of how these cells persist, enhancing T cell death in the intestinal mucosa is linked with resolution of IBD and drugs that are most effective in managing IBD function (in part), by killing pathogenic T cells resident in the gut.
Although different forms of IBD show pathophysiological and clinical differences, the therapeutic approach to managing IBD shares many common elements. Medical management of IBD is largely empirical, employing anti-inflammatory or immunosuppressive drugs. Salicylazosulfapyridine and 5-aminosalicylic acid are used to treat mild IBD and as maintenance therapy if disease remission can be achieved. Corticosteroids are used in patients with moderate to severe disease. However, clinical remission can only be obtained in ˜60% of patients, and just about half of these stay in remission after treatment is discontinued. This last point is significant because long-term use of corticosteroids carries a significant risk of serious side effects.
Immunosuppressive drugs can also be used to treat moderate to severe cases of IBD, often as a replacement for steroid therapy. However, immunosuppressive drugs (e.g., azathioprine) usually cannot ensure control of symptoms, and treatment is accompanied by numerous contraindications and severe side effects.
Drugs that often show the best efficacy in treating IBD are systemically administered (via injection or infusion) monoclonal antibodies that block TNF-alpha, a pro-inflammatory cytokine overproduced during all forms of IBD (e.g., UC, CD, graft-versus-host disease, celiac disease, iatrogenic colitis such as that induced by checkpoint inhibitors, etc.). Reducing levels of TNF-alpha in the context of IBD has two consequences. First, as an inflammatory cytokine, TNF-alpha mediates tissue damage. Second, high levels of TNF-alpha help disease causing T cells to survive and blocking TNF-alpha activity eventually leads to T cell death. Indeed, the induction of cell death by anti-TNF-alpha drugs like infliximab can predict clinical improvement in patients.
Although effective, use of anti-TNF-alpha drugs is associated with severe, systemic side effects including, re-activation of latent pathogens, hypersensitivity phenomena, cancer, and the formation of autoantibodies. Some patients are inherently resistant to anti-TNF-alpha drugs and over time, almost half of all patients that do show a response, develop resistance.
From the foregoing it is clear that there is need for new drugs to treat IBD that are more effective, less toxic, less expensive, and more convenient to administer versus standard of care.
Niclosamide (5-chloro-N-(2-chloro-4-nitrophenyl)-2-hydrobenzamide) is a halogenated salicylanilide that belongs to a group of medicines known as anthelmintics. Anthelmintics are medicines used in the treatment of worm infections. Niclosamide, which has low systemic bioavailabilty and an excellent safety profile, is used to treat broad or fish tapeworm, dwarf tapeworm, and beef tapeworm infections. It is believed that Niclosamide inhibits oxidative phosphorylation and stimulates adenosine triphosphatase activity in the mitochondria of cestodes (e.g., tapeworm), killing the scolex and proximal segments of the tapeworm both in vitro and in vivo (see, Li, Y., et al., Cancer Lett. 2014 349, 8-14.).
Recent studies have also identified other potential uses of niclosamide; e.g., as a potential anticancer agent (Id.); and as an agent for treating, preventing and/or alleviating the symptoms of type II diabetes and diabetes-related disorders or complications (see, e.g., WO 2012/068274). U.S. Pat. No. 8,148,328 discloses that niclosamide enhances the oral bioavailability of certain peptides.